The present invention pertains to conveyor systems having an endless web that is defined by laterally extending parallel cross members that are connected at opposite ends, such as by chains, and in particular to a method of correcting skew in the cross members resulting from unequal expansion of the chains on opposite sides of the web. The invention is particularly adapted for use with article sorters, but may be applied to other such conveyor systems.
An article sorter, such as the RS200 positive displacement sorter marketed by Dematic Corporation of Grand Rapids, Mich., has an endless web that is made up elongated parallel slats that are interconnected by a matched pair of chains. The web is supported by carrier wheels attached to the sides of the chains. Because of the nature of a positive displacement sorter, wear on the chains tends to not be the same. Therefore, one chain tends to stretch more than the other chain. This can cause the slats to become skewed. Skew is where the slats, which are normally perpendicular to the direction of movement of the web, become non-perpendicular to such direction. Skew causes the carrier wheels to be at an angle to the direction of movement of the web. This causes an increase in chain drag resulting in additional energy required to propel the web as well as extra wear on the sorter. Also, excessive skew of the slats can cause problems with tracking articles on the sorter and proper diverting of the articles to the desired lanes for sortation.
Uneven elongation of the chains leads to one of the chains requiring replacement prematurely. As the chains are a matched set, uneven elongation of either chain leads to both of the chains being replaced prematurely. This is very expensive because it essentially requires an almost complete disassembly of the web.